In chapter 12, Scout learns about the inequalities in educational opportunities for Blacks and Whites in Maycomb.
When Capurnia takes Scout and Jem to church with her, it really opens Scout’s eyes. She realizes that Calpurnia lives a very different life when not at their house.
The first surprise to Scout is that Cal talks differently when she is at church.
"They's my comp'ny," said Calpurnia. Again I thought her voice strange: she was talking like the rest of them. (ch 12)
Scout comments that except when she is angry, Cal has perfect grammar. She talks just as well as the white people do, and not at all in the Negro dialect. When Scout sees her amongst her own people, she realizes that Cal has to act very differently around them than she does with the Finches.
Scout is shocked when the church members sing by repeating after Zeebo reading lines. She asks Cal why the church does not save the collection money and buy hymn books.
Calpurnia laughed. "Wouldn't do any good," she said. "They can't read."
"Can't read?" I asked. "All those folks?"
"That's right," Calpurnia nodded. "Can't but about four folks in First Purchase read... I'm one of 'em." (ch 12)
Scout learns that the Finch family is the reason Cal can read. She was educated by them. She then in turn taught her son Zeebo how to read. There was no school when he was a boy.
It is clear to Scout that the black church is sorely underfunded, but she realizes that the problem is deeper. There are no educational opportunities for these people. Cal implies that they do have schools at this point, but clearly few of the people can read.